1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', 'k2s456tnutk3eqsmrt90a84ad4', '216.73.216.9', '1758067319', '1758067319', '/index.php?XTCsid=a61b1c7c4e21580bd9d4e85a32d692bc&cat=c4_Beer-Mugs.html')

[XT SQL Error]